Generally, for example as represented by the food industry, a variety of production processes include steps involving washing performed repeatedly. Such washing has conventionally used various types of detergent based on surface activity and, furthermore, biodegradation. Furthermore, in ordinary households also, foods, food utensils clothes and the like are washed by a method pursuant to the above.
Typically commercially available dish washers and sterilizers have used detergent, powdery soap or the like to wash fats and oils, protein, starch and other similar, various types of stains off utensils. Furthermore, the utensils are sterilized often with hot air, hot water or other similar thermal effects in actuality.
One example of a conventional, ordinary household dishwasher is shown in FIG. 5. In the figure, a detergent containing sodium percarbonate, sodium perborate or the like, and a proteolytic enzyme and an amylolytic enzyme blended together is previously introduced into a washing chamber 1. When the chamber is supplied with a determined amount of water, a washing pump 2 is actuated, and water for washing is inducted through a filter 3 to washing pump 2 and the water is pressurized and jetted through a nozzle. The water jetted through nozzle 4 washes utensils 6 placed in a utensil basket 5 and thereafter accumulates at a bottom of washing chamber 1 and is again inducted to washing pump 2, and thus circulates in washing chamber 1. In doing so, a heater 7 heats the water to increase the temperature thereof to increase solubility of a component of stain. Furthermore, large, insoluble leftover or the like on utensils 6 is washed off by the water and captured and removed by filter 3 when it is inducted to washing pump 2 together with the water.
After the washing operation has been completed, a drainage pump operates to discharge the water outside the dishwasher. Thereafter again a determined amount of water is supplied to washing chamber 1 and, as has been in the washing operation, the utensils are rinsed and thus washed (or washed with water circulated without detergent), and after the rinsing and washing operation has been completed the water is again drained out. Typically, this rinsing operation is performed more than once. Thereafter, heater 7 and an air blower fan 8 operate to dry the interior of washing chamber 1 and utensils 6 and the entire process thus completes. While the utensils are washed, the sodium percarbonate, sodium perborate or the like that has blended in the detergent also effectively bleaches tea stain on the utensils, decomposes odors attributed to food stains, and remove germs.
Furthermore, in the electronics industry, organic oil fouling, powdery metal, minerals, and other similar inorganic matters soiling surfaces of printed circuit boards, glass substrates and the like must be washed off. They have conventionally been washed using chlorine-based (carbon tetrachloride for example), chlorofluorocarbons-based solutions, acetone alcohol-based, organic solutions, surfactants, and the like.
However, the surfactants and, furthermore, organic solutions that have been used to wash them remain in effluents in large amounts and have thus contributed to eutrophicated rivers and oceans and other similar water pollution. Furthermore, a large amount of electricity is consumed to provide hot water, which also requires an increased amount of petroleum to generate power and by extension contributes to an increased amount of carbonic acid gas exhausted. Simultaneously, chlorine-, chlorofluorocarbons-, and organic solution-based solutions have negative effects on natural environment as well as human body, including environmental hormones.
In recent years, an electrolytic water generator has been developed to produce acidic water and alkaline water. The alkaline water produced by this apparatus decomposes protein and fats and oils and the acidic water produced thereby sterilizes germs and bleaches stains. Thus a variety of washing apparatuses have been developed with these properties made use of effectively.
For example, Japanese Patent Laying-Open No. 8-71131 proposes a washing apparatus including an electrolytic cell having a cathode and an anode therein and filled with an electrolyte. An object to be washed is immersed therein and a voltage is then applied between the cathode and the anode to pass a DC voltage through the electrolyte to wash and sterilize the object.
Furthermore, Japanese Patent Laying-Open No. 8-47473 proposes a dishwasher provided with a water creator capable of electrolyzing tap water to produce alkaline water and acidic water. The publication discusses that the apparatus's washing chamber can be supplied with the alkaline water and the acidic water selectively to wash an object with the alkaline water and sterilize it with the acidic water.
Furthermore, electrolytic chlorine water, ozone water, sterilants, and ultraviolet radiation are used in washing and sterilization, and heat, vapor and the like are used in sterilization, as disclosed for example in Japanese Patent Laying-Open Nos. 5-137689 and 8-228603.
For dishwashers, in particular, powerful synthetic detergent is generally used. This results in effluents containing a large amount of a detergent component. The effluents may insufficiently be treated in sewage disposal plants to eliminate bacteria. If the effluents are insufficiently treated, and released and flow into rivers and seas, they would have a significantly negative effect on environment. Thus there has been a demand for a method and an apparatus using the method that are developed to impose a minimize load on environment, use a detergent significantly safe for human body, and steadily and hygienically wash an object and maximally prevent effluents from contributing to pollution, eutrophication and the like.
Conventionally, however, for example as described in Japanese Patent Laying-Open No. 5-137689, bleaching utensils, decomposing odors of foods, and removing germs all depend on detergent and to minimize its environmental effects the detergent is adapted to contain less oxidative sodium percarbonate, sodium perborate or the like blended therein. As such, utensils are bleached and deodorized insufficiently. Furthermore, if foods are washed with the detergent and thereafter rinsed insufficiently or they are fresh vegetables, fruits and the like often having depressions, then carbonate, borate, or the like that corresponds to a product from a component of the detergent that has been decomposed would readily remain in and/or on the washed foods disadvantageously.
Furthermore, a conventional dishwasher sterilizes utensils at no less than 75° C. for at least two minutes when they are finally rinsed. More specifically, a household dishwasher heats water to no less than 75° C. and jets the heated water against utensils and thus rinse them for at least two minutes, thereby increasing the temperature of the utensils and thus sterilizing them. Heating the rinsing water to at least 75° C. entails supplying a large amount of electric energy and thus interferes with energy conservation.
Other washing and sterilization methods still have disadvantages in terms of persistence of bactericidal activity and stability of sterilant. For example, hypochlorous acid in an acidic state of a pH of no more than five does not exist stable for a long period of time as it rapidly decomposes and becomes chlorine gas. Furthermore it is also known that hypochlorous acid in a highly alkaline state of a pH of no less than 8.5 is slow in proceeding with a reaction producing available active chlorine through decomposition that presents bactericidal activity. To overcome such pH-dependent disadvantages to allow hypochlorous acid to present its bactericidal activity, a detergent solution needs to have a steady pH within a pH range allowing significantly steady decomposition. More specifically, a technique is required to maintain the solution within a range approximately from a pH of seven to five to maintain effective hypochlorous acid of a concentration sufficient to present bactericidal activity to provide an enhanced bactericidal effect.
As has been described above, a variety of prior arts have been disclosed in relation to washing and sterilization. There also exist hypochlorous acid and the like that are in effect used in medical institutions to wash and sterilize paths for dripped transfusion, although they do not overcome the disadvantages described above.